Lucas Auto Advance Distributors

[Charles P]

As some may know the total advance on these distributors is governed by the size of the holes in the "action plate", which sits below the base plate. 
I don't suppose anyone knows of a list of what holes sizes deliver what amount of total advance do they?

Thanks

Charles

[AustinWood]

The advance is stamped on the plate with the holes in it.

[Charles P]

Thanks Jim.
I know that but what size should the hole be if I want to convert a 10 degree plate to 14 degrees. That’s the information that I’m lacking (or a vast selection of distributors to note the degree markings and measure the holes!)

Thanks

Charles

[Chris KC]

FWIW I have a note that a DK4A (8 deg) unit had holes 8.5mm in diameter, and a DKYH4A (17 deg) had holes 10.5mm in dia.
In both cases the pin was 4.75mm dia. 
i.e. 3.75 vs 5.75mm travel.

[Charles P]

That’s useful Chris.
I have a 21 degree plate (but haven’t measured the hole yet) so may be able to interpolate the figures if the relationship proves to be linear.

[Graham Barker]

I measured the amount of advance available by twisting the distributor rotor with a protractor sitting on top of it. I then filed the holes in the plate to be oval and remeasured the advance angle. With consecutive filings followed by remeasuring the angle, I eventually obtained the amount of advance that I wanted. 
Bear in mind that one degree of advance at the distributor rotor is two degrees at the crankshaft.

[Peter Naulls]

I did the same as Graham. The holes and the pins were both slightly worn, so having first welded up the holes I filed them out bit by bit until the correct advance had been reached. I was surprised how much difference it made to the running of the car.

[Charles P]

Just to finish this off I decided to explore the current set up before taking things apart. Yes, rare, isn't it?
I bothered to make reasonably accurate marks on the mag coupling and timing case to indicate TDC. It's a bit small diameter but there's not much else to work from.
Using a clever modern timing light with advance adjustment I ascertained that the distributor on the car was not advancing correctly and was giving 38 advance in crank degrees!
I took it apart and the plate (10 cam degrees) wasn't worn but the weights and springs were not doing their job. Weights replaced and two decent light springs put in place. I timed it using the clever timing light to give 20 degrees of advance at 2,000 rpm and the result is very satisfactory. It goes so much better and keeps cooler.

The lesson is pay attention to the distributor advance mechanism.

[Peter Naulls]

A very satisfying result Charles, thanks for the update.